Internal combustion engines may be provided with a forced air system such as a turbocharger in order to increase an engine efficiency and power by forcing extra air into the combustion chamber of the cylinders. The turbocharger includes a compressor rotationally coupled to a turbine. Variable geometry turbines (VGT) are generally used, namely turbines that are equipped with a VGT actuator arranged to move a rack of vanes in different positions to alter the flow of the exhaust gases through the turbine. The turbine tends to accelerate as the vanes are closing and to decelerate as the vanes are opening.
In some automotive systems, the compressor may be assisted by an electric compressor. The electric compressor power along the maneuvers is modulated comparing a target boost memorized in a map stored in a data carrier associated with an Electronic Control Unit (ECU) of the internal combustion engine with a manifold pressure value measured by a manifold pressure and temperature sensor (TMAP) provided in the intake manifold of the engine. When a boost target is reached, the electric machine is switched off or deactivated and the boost target is maintained in steady state by the turbocharger compressor alone.
A common limitation in the achievement of high low-end torque values in turbocharged engines is represented by compressor surge phenomena. As is known in the art, compressor surge may give rise to instability phenomena that may cause disruption of the flow through the compressor. In order to prevent the occurrence of compressor surge phenomena and to achieve higher boost levels, the use of the electric compressor may be useful. However, each activation of the electric compressor has a negative impact on electric power consumption and must be planned accordingly.